<html>
<head>
  <style>
    div { background: red; height: 3em; }
    div:empty { background: lime; }
  </style>
</head>
<body>
  <div style="display: none"></div>
  <script>
    var div = document.getElementsByTagName("div")[0];
    div.appendChild(document.createTextNode(""));
    div.style.display = "";
  </script>
</body>
</html>
